docs: def arrays_to_hdf5(filename="cache.hdf5"):
      """Returns registry for serialising arrays to a HDF5 reference."""
      return Registry(
          types={
              numpy.ndarray: SerNumpyArrayToHDF5(filename, "cache.lock")
          },
          hooks={
              '<ufunc>': SerUFunc()
          },
          hook_fn=_numpy_hook
      )